U.S. patent application number 12/196911 was filed with the patent office on 2009-02-26 for semiconductor light-emitting device with selectively formed buffer layer on substrate.
This patent application is currently assigned to Miin-Jang Chen. Invention is credited to Miin-Jang Chen, Szu-Hua Ho, Wen-Ching Hsu.
Application Number | 20090050914 12/196911 |
Document ID | / |
Family ID | 40381335 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090050914 |
Kind Code |
A1 |
Chen; Miin-Jang ; et
al. |
February 26, 2009 |
SEMICONDUCTOR LIGHT-EMITTING DEVICE WITH SELECTIVELY FORMED BUFFER
LAYER ON SUBSTRATE
Abstract
The invention discloses a semiconductor light-emitting device
and a method of fabricating the same. The semiconductor
light-emitting device according to the invention includes a
substrate, a buffer layer, a multi-layer structure, and an ohmic
electrode structure. The buffer layer is selectively formed on an
upper surface of the substrate such that the upper surface of the
substrate is partially exposed. The multi-layer structure is formed
to overlay the buffer layer and the exposed upper surface of the
substrate. The multi-layer structure includes a light-emitting
region. The buffer layer assists a bottom-most layer of the
multi-layer structure in lateral and vertical epitaxial growth. The
ohmic electrode structure is formed on the multi-layer
structure.
Inventors: |
Chen; Miin-Jang; (Taipei
City, TW) ; Hsu; Wen-Ching; (Hsinchu City, TW)
; Ho; Szu-Hua; (Jhudong Township, TW) |
Correspondence
Address: |
Muncy, Geissler, Olds & Lowe, PLLC
P.O. BOX 1364
FAIRFAX
VA
22038-1364
US
|
Assignee: |
Chen; Miin-Jang
Taipei City
TW
Sino-American Silicon Products Inc. & CHEN,
Miin-Jang
Hsinchu
TW
|
Family ID: |
40381335 |
Appl. No.: |
12/196911 |
Filed: |
August 22, 2008 |
Current U.S.
Class: |
257/94 ;
257/E33.014; 438/47 |
Current CPC
Class: |
H01L 33/12 20130101;
H01L 33/007 20130101 |
Class at
Publication: |
257/94 ; 438/47;
257/E33.014 |
International
Class: |
H01L 33/00 20060101
H01L033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 24, 2007 |
TW |
096131337 |
Claims
1. A semiconductor light-emitting device, comprising: a substrate;
a buffer layer, selectively formed on an upper surface of the
substrate such that the upper surface of the substrate is partially
exposed; a multi-layer structure, formed to overlay the buffer
layer and the exposed upper surface of the substrate, the
multi-layer structure comprising a light-emitting region, wherein
the buffer layer assists a bottom-most layer of the multi-layer
structure in lateral and vertical epitaxial growth; and an ohmic
electrode structure, formed on the multi-layer structure.
2. The semiconductor light-emitting device of claim 1, wherein the
buffer layer is made of a material selected from the group
consisting of ZnO, Mg.sub.xZn.sub.1-xO, AlN and Al.sub.2O.sub.3,
where 0<x.ltoreq.1.
3. The semiconductor light-emitting device of claim 2, wherein the
bottom-most layer is made of GaN.
4. The semiconductor light-emitting device of claim 2, wherein the
buffer layer has a thickness in a range of 10 nm to 500 nm.
5. The semiconductor light-emitting device of claim 3, wherein the
buffer layer is formed by an atomic layer deposition process and/or
a plasma-enhanced (or a plasma-assisted) atomic layer deposition
process.
6. The semiconductor light-emitting device of claim 4, wherein the
formation of the buffer layer is through a selective etching
process.
7. The semiconductor light-emitting device of claim 5, wherein the
formation of the buffer layer is performed at a processing
temperature ranging from room temperature to 1200.degree. C.
8. The semiconductor light-emitting device of claim 6, wherein the
buffer layer is further annealed at a temperature ranging from
400.degree. C. to 1200.degree. C. after formed.
9. The semiconductor light-emitting device of claim 7, wherein the
precursors of the buffer layer of ZnO are ZnCl.sub.2, ZnMe.sub.2,
ZnEt.sub.2, and H.sub.2O, O.sub.3, O.sub.2 plasma, or an oxygen
radical.
10. The semiconductor light-emitting device of claim 7, wherein the
precursors of the buffer layer of Mg.sub.xZn.sub.1-xO are
ZnCl.sub.2, ZnMe.sub.2, ZnEt.sub.2, MgCp.sub.2, Mg(thd).sub.2, and
H.sub.2O, O.sub.3, O.sub.2 plasma, or an oxygen radical.
11. The semiconductor light-emitting device of claim 7, wherein the
precursors of AlN are NH.sub.3 and AlCl.sub.3, AlMe.sub.3,
AlEt.sub.3, Me.sub.3N:AlH.sub.3, or Me.sub.2EtN:AlH.sub.3.
12. The semiconductor light-emitting device of claim 7, wherein the
precursors of Al.sub.2O.sub.3 are AlCl.sub.3, AlBr.sub.3,
AlMe.sub.3, AlEt.sub.3, and H.sub.2O, O.sub.3, O.sub.2 plasma, or
an oxygen radical.
13. The semiconductor light-emitting device of claim 1, wherein the
substrate is made of a material selected from the group consisting
of sapphire, Si, SiC, GaN, ZnO, ScAlMgO.sub.4, YSZ
(Yttria-Stabilized Zirconia), SrCu.sub.2O.sub.2, LiGaO.sub.2,
LiAlO.sub.2, and GaAs.
14. A method of fabricating a semiconductor light-emitting device,
comprising the steps of: preparing a substrate; selectively forming
a buffer layer on an upper surface of the substrate such the upper
surface of the substrate is partially exposed; forming a
multi-layer structure to overlay the buffer layer and the exposed
upper surface of the substrate, wherein the multi-layer structure
comprises a light-emitting region, and the buffer layer assists a
bottom-most layer of the multi-layer structure in lateral and
vertical epitaxial growth; and forming an ohmic electrode structure
on the multi-layer structure.
15. The method of claim 14, wherein the buffer layer is made of a
material selected from the group consisting of ZnO,
Mg.sub.xZn.sub.1-xO, AlN and Al.sub.2O.sub.3, where
0<x.ltoreq.1.
16. The method of claim 15, wherein the bottom-most layer is made
of GaN.
17. The method of claim 15, wherein the buffer layer has a
thickness in a range of 10 nm to 500 nm.
18. The method of claim 17, wherein the buffer layer is formed by
an atomic layer deposition process and/or a plasma-enhanced (or a
plasma-assisted) atomic layer deposition process.
19. The method of claim 17, wherein the formation of the buffer
layer is through a selective etching process.
20. The method of claim 18, wherein the formation of the buffer
layer is performed at a processing temperature ranging from room
temperature to 1200.degree. C.
21. The method of claim 20, wherein the buffer layer is further
annealed at a temperature ranging from 400.degree. C. to
1200.degree. C. after formed.
22. The method of claim 20, wherein the precursors of the buffer
layer of ZnO are ZnCl.sub.2, ZnMe.sub.2, ZnEt.sub.2, and H.sub.2O,
O.sub.3, O.sub.2 plasma, or an oxygen radical.
23. The method of claim 20, wherein the precursors of the buffer
layer of Mg.sub.xZn.sub.1-xO are ZnCl.sub.2, ZnMe.sub.2,
ZnEt.sub.2, MgCp.sub.2, Mg(thd).sub.2, and H.sub.2O, O.sub.3,
O.sub.2 plasma, or an oxygen radical.
24. The method of claim 20, wherein the precursors of AlN are
NH.sub.3 and AlCl.sub.3, AlMe.sub.3, AlEt.sub.3,
Me.sub.3N:AlH.sub.3, or Me.sub.2EtN:AlH.sub.3.
25. The method of claim 20, wherein the precursors of
Al.sub.2O.sub.3 are AlCl.sub.3, AlBr.sub.3, AlMe.sub.3, AlEt.sub.3,
and H.sub.2O, O.sub.3, O.sub.2 plasma, or an oxygen radical.
26. The method of claim 14, wherein the substrate is made of a
material selected from the group consisting of sapphire, Si, SiC,
GaN, ZnO, ScAlMgO.sub.4, YSZ (Yttria-Stabilized Zirconia),
SrCu.sub.2O.sub.2, LiGaO.sub.2, LiAlO.sub.2, and GaAs.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a semiconductor
light-emitting device and, more particularly, to a semiconductor
light-emitting device with an enhanced external quantum efficiency
and a good epitaxy quality.
[0003] 2. Description of the Prior Art
[0004] The current semiconductor light-emitting devices, such as
light-emitting diodes, have been used for a wide variety of
applications, e.g. illuminations and remote controls. To ensure
high functional reliability as great as possible and a low power
requirement of the semiconductor light-emitting devices, the
external quantum efficiency is required for the devices.
[0005] In principle, the external quantum efficiency of a
semiconductor light-emitting device is determined both by the
internal quantum efficiency and extraction efficiency. The internal
quantum efficiency is determined by the material property and
quality. The extraction efficiency refers to the proportion of
radiation emitted from the interior of the device into the
surrounding air or encapsulating epoxy. The extraction efficiency
is determined by the losses occurred when radiation leaves the
interior of the device. One of the main causes for such losses is
the high refractive index of the semiconductor material so the
radiation cannot be emitted outside at the semiconductor surface on
account of total reflection.
[0006] Please refer to FIG. 1. To enhance the external quantum
efficiency of the semiconductor light-emitting device, a sapphire
substrate 1 with a patterned surface 10 has been disclosed and
applied to the manufacture of the semiconductor light-emitting
device. FIG. 1 illustrates a schematic view of a conventional
sapphire substrate 1 with a patterned surface 10. The patterned
surface 10 is for scattering light emitted out from the
semiconductor light-emitting device to reduce the probability of a
total reflection, and further to enhance the external quantum
efficiency of the semiconductor light-emitting device.
[0007] Although a semiconductor material layer, e.g. a GaN layer,
can be formed on the patterned surface 10 of the sapphire substrate
1 through a good lateral epitaxial growth, the GaN layer can not be
grown on the patterned surface 10 of the sapphire substrate 1
directly, i.e. a poor vertical epitaxial growth. Therefore, the
quality of the GaN semiconductor material layer formed on the
patterned surface 10 of the sapphire substrate 1 is still required
for improvement.
[0008] Inside the semiconductor light-emitting device of the prior
art, a buffer layer can be formed between a semiconductor material
layer and an ordinary substrate to improve the quality of the
semiconductor material layer. As a result, the external quantum
efficiency of the semiconductor light-emitting device will further
be enhanced by the buffer layer.
[0009] Accordingly, the main scope of the invention is to provide a
semiconductor light-emitting device with an enhanced external
quantum efficiency and a good epitaxy quality.
SUMMARY OF THE INVENTION
[0010] One scope of the invention is to provide a semiconductor
light-emitting device and a fabricating method thereof.
[0011] According to an embodiment of the invention, the
semiconductor light-emitting device includes a substrate, a buffer
layer, a multi-layer structure, and an ohmic electrode
structure.
[0012] The buffer layer is selectively formed on an upper surface
of the substrate such that the upper surface of the substrate is
partially exposed. The multi-layer structure is formed to overlay
the buffer layer and the exposed upper surface of the substrate.
The multi-layer structure includes a light-emitting region. The
buffer layer is formed to assist a bottom-most layer of the
multi-layer structure in lateral and vertical epitaxial growth. The
ohmic electrode structure is formed on the multi-layer
structure.
[0013] According to another embodiment of the invention, it is
related to a method of fabricating a semiconductor light-emitting
device.
[0014] First, a substrate is prepared. Subsequently, a buffer layer
is formed on an upper surface of the substrate selectively such the
upper surface of the substrate is partially exposed. Then, a
multi-layer structure is formed to overlay the buffer layer and the
exposed upper surface of the substrate. The multi-layer structure
includes a light-emitting region, and the buffer layer is formed to
assist a bottom-most layer of the multi-layer structure in lateral
and vertical epitaxial growth. Finally, an ohmic electrode
structure is formed on the multi-layer structure.
[0015] Compared to the prior art, the buffer layer of the
semiconductor light-emitting device according to the invention is
selectively formed on the substrate and is for scattering light
emitted from the semiconductor light-emitting device to reduce the
total reflection and further enhance the external quantum
efficiency of the semiconductor light-emitting device. Furthermore,
the buffer layer can assist a bottom-most layer of the multi-layer
structure in lateral and vertical epitaxial growth to increase the
epitaxy quality of the semiconductor light-emitting device.
[0016] The advantage and spirit of the invention may be understood
by the following recitations together with the appended
drawings.
BRIEF DESCRIPTION OF THE APPENDED DRAWINGS
[0017] FIG. 1 illustrates a schematic view of a conventional
sapphire substrate with a patterned surface.
[0018] FIG. 2 illustrates a sectional view of a semiconductor
light-emitting device according to an embodiment of the
invention.
[0019] FIGS. 3A through 3I illustrate sectional views to describe a
method of fabricating a semiconductor light-emitting device
according to another embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Please refer to FIG. 2. FIG. 2 illustrates a sectional view
of a semiconductor light-emitting device 2 according to an
embodiment of the invention. As shown in FIG. 2, the semiconductor
light-emitting device 2 includes a substrate 20, a buffer layer 22,
a multi-layer structure 24, and an ohmic electrode structure
26.
[0021] In practical applications, the substrate 20 can be made of
sapphire, Si, SiC, GaN, ZnO, ScAlMgO.sub.4, YSZ (Yttria-Stabilized
Zirconia), SrCu.sub.2O.sub.2, LiGaO.sub.2, LiAlO.sub.2, GaAs and
the like.
[0022] The buffer layer 22 is selectively formed on an upper
surface 200 of the substrate 20 such that the upper surface 200 of
the substrate 20 is partially exposed. The multi-layer structure 24
is formed to overlay the buffer layer 22 and the exposed upper
surface 200 of the substrate 20. The multi-layer structure 24
includes a light-emitting region 242. The buffer layer 22 is formed
to assist a bottom-most layer 240 of the multi-layer structure 24
in lateral and vertical epitaxial growth. In one embodiment, the
bottom-most layer 240 can be made of GaN. The ohmic electrode
structure 26 is formed on the multi-layer structure 24.
[0023] In practical applications, the buffer layer 22 can be made
of ZnO, Mg.sub.xZn.sub.1-xO, AlN or Al.sub.2O.sub.3, where
0<x.ltoreq.1. In addition, the buffer layer 22 can have a
thickness in a range of 10 nm to 500 nm.
[0024] If the buffer layer 22 is made of ZnO, the precursors of the
ZnO buffer layer 22 can be ZnCl.sub.2, ZnMe.sub.2, ZnEt.sub.2, and
H.sub.2O, O.sub.3, O.sub.2 plasma, or an oxygen radical. If the
buffer layer 22 is made of Mg.sub.xZn.sub.1-xO, the precursors of
the Mg.sub.xZn.sub.1-xO buffer layer 22 can be ZnCl.sub.2,
ZnMe.sub.2, ZnEt.sub.2, MgCp.sub.2, Mg(thd).sub.2, and H.sub.2O,
O.sub.3, O.sub.2 plasma, or an oxygen radical. If the buffer layer
22 is made of AlN, the precursors of the AlN buffer layer 22 can be
NH.sub.3 and AlCl.sub.3, AlMe.sub.3, AlEt.sub.3,
Me.sub.3N:AlH.sub.3, or Me.sub.2EtN:AlH.sub.3. If the buffer layer
22 is made of Al.sub.2O.sub.3, the precursors of the
Al.sub.2O.sub.3 buffer layer 22 can be the precursors of
Al.sub.2O.sub.3 are AlCl.sub.3, AlBr.sub.3, AlMe.sub.3, AlEt.sub.3,
and H.sub.2O, O.sub.3, O.sub.2 plasma, or an oxygen radical.
[0025] In one embodiment, the buffer layer 22 can be formed by an
atomic layer deposition process and/or a plasma-enhanced (or a
plasma-assisted) atomic layer deposition process. Moreover, the
formation of the buffer layer 22 can be performed at a processing
temperature ranging from room temperature to 1200.degree. C.
Further, the buffer layer 22 can be annealed at a temperature
ranging from 400.degree. C. to 1200.degree. C. In another
embodiment, the formation of the buffer layer 22 can be through a
selective etching process.
[0026] Please refer to FIGS. 3A through 3I. FIGS. 3A through 3I
illustrate sectional views to describe a method of fabricating a
semiconductor light-emitting device according to another embodiment
of the invention.
[0027] First, a substrate 20 is prepared, as shown in FIG. 3A.
Subsequently, as shown in FIG. 3B, a buffer layer 22 can be formed
on an upper surface 200 of the substrate 20 by an atomic layer
deposition process in one embodiment. Then, an etching-resistant
layer (e.g. a photoresist layer) 23 can be selectively formed on
the surface of the buffer layer 22 as shown in FIG. 3C, and a
selective etching process is performed on the surface of the buffer
layer 22. Accordingly, the buffer layer 22 can be selectively
formed on the upper surface 200 of the substrate 20 such that the
upper surface 200 of the substrate 20 is partially exposed, as
shown in FIG. 3D.
[0028] In another embodiment, an etching-resistant layer (e.g. a
photoresist layer) 23 can be formed on the upper surface 200 of the
substrate 20, as shown in FIG. 3E. Next, a buffer layer 22 can be
formed on the upper surface 200 of the substrate 20 by an atomic
layer deposition process and/or a plasma-enhanced (or a
plasma-assisted) atomic layer deposition process, as shown in FIG.
3F. Then, a lift-off process can be implemented to remove the
etching-resistant layer 23 to selectively form the buffer layer 22
on the upper surface 200 of the substrate 20 such that the upper
surface 200 of the substrate 20 is partially exposed, as shown in
FIG. 3G.
[0029] Subsequently, a multi-layer structure 24 is formed to
overlay the buffer layer 22 and the exposed upper surface 200 of
the substrate 20, as shown in FIG. 3H. The multi-layer structure 24
includes a light-emitting region 242, and the buffer layer 22 is
formed to assist a bottom-most layer 240 of the multi-layer
structure 24 in lateral and vertical epitaxial growth. Finally, the
multi-layer structure 24 can be selectively etched, and then an
ohmic electrode structure 26 is formed on the multi-layer structure
24, as shown in FIG. 3I.
[0030] Compared to the prior art, the buffer layer of the
semiconductor light-emitting device according to the invention is
selectively formed on the substrate and for scattering light
emitted from the semiconductor light-emitting device to reduce the
total reflection and further enhance the external quantum
efficiency of the semiconductor light-emitting device. Furthermore,
the buffer layer can assist a bottom-most layer of the multi-layer
structure in lateral and vertical epitaxial growth to increase the
epitaxy quality of the semiconductor light-emitting device.
[0031] With the example and explanations above, the features and
spirits of the invention will be hopefully well described. Those
skilled in the art will readily observe that numerous modifications
and alterations of the device may be made while retaining the
teaching of the invention. Accordingly, the above disclosure should
be construed as limited only by the metes and bounds of the
appended claims.
* * * * *